1. Field of the Invention
This invention relates to a method for laying a wire in a junction box to form conductive circuits in the junction box which is used in, for example, electrical wiring for a motorcar.
2. Statement of the Prior Art
In a connecting assembly, in the so-called joint box or junction box (hereinafter referred to as "junction box") used in the electrical wiring in a motorcar, heretofore, the conductive circuits in the junction box were generally constructed by bus bars. However, very expensive dies and a large press machine are required to make the bus bars and many unnecessary portions are left in a blank metal sheet after it is punched, thereby making the bus bars costly. Further, the bus bars lack an antileak characteristic since they expose their conductive faces. Consequently, as disclosed in, for example, unexamined Japanese Patent Public Disclosure No. 63-313475 (1988), a joint box has recently been proposed in which the conductive circuits are made of covered electrical wires.
Heretofore, when the conductive circuits are made of covered wire, the wire is cut in lengths corresponding to each of tile conductive circuits so that these cut wires are coupled to connecting terminals in the joint box.
However, since this process is very complicated and takes a lot of time, the method disclosed in examined Japanese Public Publication No. 3-76086 (1991) was proposed to overcome this problem. In this method a path is formed by a plurality of protrusions on the insulation base and wire-coupling portions of the connecting terminals. The wire is laid on the insulation base in each of the conductive circuits by moving a wire-feeder along the path while feeding the wire to the insulation base and pushing the fed wire between the protrusions or into the wire-coupling portions of the connecting terminals. In this method, the wire is electrically contacted with the connecting terminals by pushing the wire into the wire-coupling portions. Also, In the method, the wire is cut when a circuit is formed by a single wire and the above operation is repeated at every circuit.
However, the method disclosed in the above publication causes the following problems.
First, since in the above method the wire is cut when the circuit is formed by a single wire, the feeding of the wire and the movement of the wire-feeder must be stopped at every cutting time and the wire-feeder must be displaced between a working station and non-working station on the insulation base. Thus, it takes a lot of time to make a circuit from one to the other, it is impossible to carry out a wiring while maintaining the wire-feeder at a high speed, and it is difficult to improve working efficiency.
Second, since a covered electrical wire with a single highly rigid core is used to form the conductive circuits in order to maintain a certain shape, a relatively strong force is required to bend the highly rigid wire into a desired shape. However, the protrusions forming the path are not strong enough to bend the wire since the insulation base is made of a synthetic resin. Consequently, the method disclosed in Japanese Publication No. 3-76086 causes the wire-feeder to be turned at the positions where the wire is to be bent so that a strong load is not applied to the protrusions.
Thus, the method disclosed in the above publication requires a mechanism which forcibly rotates the wire-feeder. This mechanism is expensive. Also, the working speed must be suppressed so that a strong impact is not applied to the protrusions. This makes it difficult to improve working efficiency.
In addition, since the path to guide the wire must be formed in the insulation base in the method disclosed in the above publication, it is difficult to make the base small, thereby making the junction box too large.